This invention relates to a process and an apparatus for treating the surfaces of friction rollers for open-end friction spinning units which are each equipped with two rollers adjacent one another and forming a wedge-shaped gap.
In the operation of an open-end friction spinning unit, the distance between the rollers forming the wedge-shaped gap in which the yarn is formed is of considerable importance. In order to be able to spin a relatively fine yarn, the wedge-shaped gap must be relatively narrow. For this purpose, the rollers are arranged at a distance from one another of only a few hundredths of a millimeter. Also, the wedge-shaped gap must not change its width during the operation, i.e., each roller surface must have precise concentricity relative to its axis of rotation. If the rollers are not completely round, the width of the wedge-shaped gap will change constantly so that the friction characteristics in the wedge-shaped gap will change correspondingly. With the changing friction characteristics, the twist applied to the yarn also changes, thereby resulting in the danger that thick and thin points may occur in the yarn.
An objective of the present invention is to provide a process and apparatus for treating the surfaces of rollers by which the concentricity of the rollers can be made more precise.
This objective is achieved according to the invention by treating the surfaces of two rollers jointly during at least the last roller preparing cycle and installing these two rollers as a pair in one spinning unit.
By means of the joint treatment of their surfaces, the rollers are mated with one another. By then installing them together for use in one spinning unit, problems due to the use of two rollers which may each have large surface irregularities are avoided.
In one aspect of the present invention, two rollers are mounted, driven and simultaneously treated by a polishing or grinding element in a position that corresponds to their operational position in a spinning unit. This apsect is advantageous because during the treating, the two rollers take up their later operational orientation with respect to one another resulting in a further increase of the precision of concentricity. In this case, it is especially advantageous to press the two rollers with biasing means against a polishing or grinding means disposed between them. As a result during the polishing or grinding phase, out of round conditions in the rollers are diminished.
It is contemplated that rollers be driven at speeds that differ from one another during their surface treatment. This ensures that during turning the same points of the two rollers are not always opposite one another. In this way slight indentations or elevations in the roller surfaces are not increased, but are actually diminished.
It is further contemplated that the rollers are driven in the same rotational direction. The rollers therefore move in relation to one another in a manner that is similar to their later operation in the spinning unit.
In a further development of the invention, the polishing or grinding means is driven at a speed that differs from the circumferential speed of the rollers. This ensures that the polishing or grinding means is always applied to different areas on the surfaces of the rollers so that over an extended period of time, a uniform method of operation of the polishing or grinding means can be ensured.
In an especially advantageous development of the invention, the rollers are combined with bearings to form one structural unit and are treated in this condition before carrying out the last treatment phase of their surfaces. As a result, those out of round errors that may possibly be caused by their bearings will be worked off in the last roller preparing cycle.
In a further development of the invention, in order to provide an apparatus for treating the surfaces of rollers, receiving means are provided for receiving two rollers in an orientation with respect to one another that corresponds to their operational orientation in a spinning unit. Also provided are drives for the two rollers and at least one polishing or grinding element for simultaneously treating the surfaces of both rollers. By means of this apparatus, the two rollers that will later be used jointly in a spinning unit are treated in such a way that a high measure of mutual concentricity is obtained at least during the last preparing cycle which determines the final shape of their surfaces.
In a further development of the invention, it is provided that the receiving means are biased in such a way that the two rollers rest against the polishing or grinding element disposed between them with a predetermined force. As a result, a uniform effect on the surfaces of both rollers due to the polishing or grinding means is obtained.
In a further development of the invention, it is provided that between the receiving means of the rollers, a belt is arranged that is equipped with a polishing or grinding coating on both sides. Advantageously, the belt is designed as a rotating driven continuous loop, resulting in a simple and reliably operating apparatus. It is advantageous in this case that the width of the belt corresponds to the length of the surfaces of the rollers to be treated. This results in a uniform treatment of the surfaces, especially the area which later is opposite the mouth of a fiber feeding channel when the rollers are positioned within the spinning unit. It is in this vicinity that the actual formation of the yarn takes place.
In a further development of the invention, the rollers are disposed on shafts that can be clamped into the receiving means. In this case, it is especially advantageous that tube-shaped suction inserts are provided as shafts on which the rollers, designed as cylinders, are disposed by means of roller bearings. The receiving means are designed corresponding to the holders of the suction inserts of a spinning unit. Thus the rollers are completely combined with their bearings and shafts before they are subjected to the last treatment. Imprecisions with respect to concentricity caused by the bearings and shafts will therefore also be eliminated.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, embodiments constructed in accordance with the present invention.